1. Field of the Invention
The present invention relates to a tape cartridge accommodating a rolled length of magnetic recording tape and, more particularly, to a tape cartridge having a reel lock mechanism to keep reels immovable when the tape cartridge is not in use.
2. Description of the Related Art
DAT tape cartridges, that is, tape cartridges specifically designed for use with a digital audio tape (DAT) player, are generally provided with a reel lock mechanism to keep reels immovable when the tape cartridge is not in use. This type of reel lock mechanism is disclosed in, for example, Japanese Laid-open Utility Model Publication No. 63-191483, published in 1988, and this known reel lock mechanism will now be discussed with the aid of FIGS. 20a and 20b of the drawings annexed hereto.
As is well known, the tape cartridge of the type to which the present invention pertains is generally standardized in size and configuration so that it can be used with the commercially available digital audio tape player. This tape cartridge comprises a generally rectangular box-like casing 1 including rectangular top and bottom walls and a peripheral wall disposed between the top and bottom walls to keep the top and bottom walls spaced apart a distance enough to accommodate a length of magnetic recording tape within the casing, the peripheral wall including a hingedly supported front wall section or front cover 6, a rear wall section opposite to the front cover and a pair of side wall sections, all assembled together with the top and bottom walls to render the cartridge to represent a generally rectangular, generally flattened box-like configuration.
In practice, the casing 1 is divided into two casing halves along a plane generally intermediate of the thickness of the peripheral wall.
Within the casing 1, there is disposed a pair of freely rotatable reels 3, each generally in the form of a cylindrical hub, to which opposite ends of the length of magnetic recording tape 2 are anchored respectively, and a pair of guide rollers 5 rotatably disposed within the casing 1 at respective corner areas adjacent the front cover 6 so as to permit a portion of the length of magnetic recording tape 2 between the guide rollers 5 to extend generally parallel to the front cover 6.
As shown in FIGS. 20a and 20b, the reel lock mechanism employed in the prior art DAT tape cartridge is housed within the casing 1 and is cooperable with any one of toothed lock wheels 8 each formed integrally with one end of the associated reel 3. This reel lock mechanism includes a generally elongated, thin-walled lock member 9 extending widthwise of the casing 1 and between the opposite side wall sections of the casing 1 for movement between unlocked and locked positions in a direction perpendicular to the lengthwise direction of the lock member 9. The lock member 9 has lock pawls 11 formed integrally therewith so as to protrude outwardly therefrom for engagement with the corresponding toothed lock wheels 8 integral with the respective reels 3.
The lock member 9 is normally biased towards the lock position by a wire spring 10 and has its opposite ends connected or integrally formed with respective traction arms 12 extending perpendicular to the lock member 9. Respective free ends of the traction arms 12 are operatively associated with the front cover 6 so that, when the front cover 6 is opened to allow that portion of the length of magnetic recording tape 2 to be exposed to the outside, the lock member 9 can be retraced against the resiliency of the wire spring 10 towards the unlock position with the lock pawls 11 consequently disengaging from the associated toothed lock wheels 8, but when the front cover 6 is closed to conceal that portion of the length of magnetic recording tape 2, the lock member 9 can be urged by the wire spring 10 to the lock position with the lock pawls 11 consequently engaged with the toothed lock wheels 8.
To operatively couple the free ends of the front cover 6, respective hinge arms 6b protruding transversely from opposite ends of the front cover 6 have their inner surfaces formed with associated operating ribs 16. So long as the lock member 9 is held in the lock position, the lock pawls 11 are engaged with the associated toothed lock wheels 8 integral with the reels 3 and, therefore, the reels 3 are held immovable to avoid any possible loosening of the length of magnetic recording tape 2.
With the reel lock mechanism wherein the biasing force of the wire spring 10 is utilized to keep the lock member 9 in the lock position, the lock pawls 11 integral with the lock member 9 will not disengage from the associated toothed lock wheels 8 so long as the tape cartridge is handled normally. However, when an excessive external force such as an impact on the tape cartridge as a result of, for example, an accidental fall of the tape cartridge onto an indoor or outdoor ground surface, the reels 3 may be instantaneously rattled enough to cause the lock member 9 to be undesirably displaced against the resiliency of the wire spring 10. Once this occur, the lock pawls 11 are disengaged from the associated toothed lock wheels 8, permitting the reels 3 to rotate idle, resulting in a loosening of the length of magnetic recording tape 2 that is turned around those reels 3.
When the tape cartridge in which the length of magnetic recording tape 2 has been loosened in the manner described above is loaded into a digital audio tape player, the length of magnetic recording tape may be undesirably bent and/or caught by loading pins employed in the digital audio tape player to pull that portion of the length of magnetic recording tape outwardly from the casing, eventually resulting in a detrimental problem in that the tape cartridge may be no longer usable and/or a tape loading mechanism in the digital audio tape player may be impaired.